I find it easiest to rough out the figure in modelling clay. Here I am using a full body figure standing behind the mechanism.
Using the clay I can quickly get the proportions and size right. The flexibility of the clay also helps me to decide what movements will work.
Previously I have either gone straight to carving in wood from the clay model or have made a more finished model in polymer clay and used this on my DIY copy carver to produce the final wooden figure.
This time I will make the model in software using Blender, an open source 3D design programme. I will then use OpenScad, another open source 3D programme to split the model up and design the joints. That is the theory anyway.